Introduction

In the past years Sigma has offered one of the most attractive options regarding ultra wide angle lenses for APS-C cameras. The 10-20 mm f/4.0-5.6 EX combines an attractive price with very good optical performance.That's why it came by surprise for many when Sigma announced another UWA zoom, with the same zoom range, but a little faster this time: f/3.5 throughout the whole zoom range. The larger aperture of course means the lens itself has become larger and heavier, as well as more expensive than its slower sibling.

The build quality of the lens is excellent. It features the crinkle style finish typical for Sigma EX lenses, both zoom and focus ring are damped, the latter a little stiff, though. Thanks to a sonic wave driven AF (which Sigma calls HSM) the lens features autofocus on all current Nikon DX DSLRs (including the motor free entry level cameras). Typical for a HSM drive, focus can be manually overridden at any time.

The lens doesn't feature an aperture ring (a G-type lens).

The lens extends a little when zooming. It's shortest at around 15 mm, slightly extended at 20 mm and at maximum length at 10 mm. The moving inner tube is very solid, there is no wobbling. The front lens does not rotate while focusing so using a polarizer is no problem. However, the front thread requires large (and expensive) 82 mm filters.

If you're used to Nikkor lenses, the Sigma's zoom and focus ring turn in the "wrong" direction (users of the Canon mount variant will naturally disagree here).

A minor upgrade over its older sibling is the addition of an AF/M switch.